Cavitation Processing Method

This application claims the benefit of priority to Japanese Patent Application No. 2024-101269, filed on Jun. 24, 2024, the entire contents of which are hereby incorporated by reference.

The present invention relates to a cavitation processing method for performing cavitation processing on a workpiece.

A cavitation surface processing method called cavitation abrasive surface finishing (CASF) is known in which a cavitation jet containing abrasives is used to smooth and peen a surface of the workpiece (US 2024/0001509 A1).

According to the conventional cavitation processing method, an inside of a curved target hole cannot be ground in some cases.

An object of the present invention is to efficiently grind the inside of the target hole curved from an inlet to an outlet.

A first aspect of the present invention provides a cavitation processing method, including:

The workpiece is made of metal. The metal constituting the workpiece is, for example, a heat-resistant alloy, an aluminum alloy, a magnesium alloy, titanium, a titanium alloy, steel, or corrosion-resistant steel. The workpiece is, for example, a mechanical part, a medical device part, or a medical device. The mechanical part is, for example, a pipe, a valve, a pipe fitting, and an aerospace part. The medical device includes a surgical implant. An aerospace component includes an aircraft engine component and other aircraft components, a rocket engine component, a spacecraft component, a satellite component, and a rocket piping.

The target hole may be a through hole. The target hole may extend linearly from the inlet and have a curved portion on a back side thereof. The target hole may only have a curved portion.

The nozzle diameter is, for example, 0.5 mm to 3 mm. The ejection pressure of the jet is, for example, 10 MPa to 200 MPa.

Both the workpiece and the nozzle are immersed in the processing liquid stored in the tank. In the processing liquid, the jet of the processing liquid is ejected from the nozzle toward the workpiece. The processing liquid is, for example, water. The processing liquid may include a rust inhibitor.

The ejection axis may be in contact with an inner side surface of the curved portion. The ejection axis may intersect an outer side surface which is an outer peripheral side surface of the curved portion. The ejection axis may have a portion that passes in the vicinity of the inner side surface from the outer side surface of the curved portion. The ejection axis may extend along the inner side surface on the outlet side from the inlet side end of the curved portion. The ejection axis may extend along the inner side surface at the outlet side end of the curved portion.

The cavitation processing is performed on a part or the entire surface of the side surface of the target hole.

The abrasives are abrasive particles. Examples of the abrasives include ceramics, alumina, garnet, and zirconia.

The structure of the support structure is, for example, block support, adaptive cell support, rod support, line support, and tree support.

The jet may remove the support structure while smoothing the sides of the target holes being supported.

According to the present invention, it is possible to efficiently grind the inside of the target hole curved from the inlet to the outlet.

In the cavitation processing method according to a first embodiment, a workpieceis firstly shaped by additive manufacturing. Next, the workpieceand a nozzleare immersed in a processing liquidin which abrasivesare suspended. Then, a support structureis removed by cavitation processing.

The workpieceaccording to the present embodiment will be described with reference to.is a cross-sectional view taken along line I-I in. In, an X direction and a Y direction are horizontal directions. A Z direction is a vertical direction. A description will be given based on a posture of the workpiecewhen the cavitation processing is performed.

The workpiecehas an upper surface, a lower surface, and a single target hole. The upper surfacefaces upwards. The lower surfacefaces downward. The upper surfaceand the lower surfacemay be parallel to each other. The target holehas an inlet, an outlet, and a side surface. The target holepenetrates from the upper surfaceto the lower surface. The inletis formed on the upper surface. The outletis formed on the lower surface. The outletis located on the back side with respect to the inlet. The side surfaceextends from the inletto the outlet. As shown in, the target holeis elongated along the X direction as viewed from the upper side.

As shown in, the target holehas a curved portion. The target holedoes not have a support structure. The curved portionis curved from the inletto the outlet. The entire target holeis the curved portion. The curved portionis curved such that the outletis visible from the inlet. The curved portionincludes an inner side surfaceand an outer side surface. The inner side surfaceis an inner peripheral side (right side in) of the curved portion. The outer side surfaceis an outer peripheral side (left side in) of the curved portion. As shown in, on a plane orthogonal to the X direction, a tangent line T passing through an end portion of the inner side surfaceon the outletside extends in the vertical direction.

In the target hole, an ejection axisis defined as follows. The ejection axisis defined in a cross section of the target holeorthogonal to the X direction. As shown in, the ejection axisis a straight line extending from the outside of the target holeto the inside through the inlet. The ejection axishas a portion closer to the inner side surfaceon the outletside than on the inletside of the target hole. At least at the end of the target holeon the outletside, the ejection axispasses closer to the inner side surfacethan the outer side surface. The ejection axisextends along the inner side surfaceat the end of the target holeon the outletside. The ejection axisextends vertically downward.

First, the workpieceis shaped by additive manufacturing. As shown in, a material is laminated from below on a base surface, and the lower surfaceis in contact with the base surface. At the time of shaping, a surface of the side surfacesof the target holefacing upward is referred to as an up skin surface, and a surface of the side surfacesof the target holefacing downward is referred to as a down skin surface. The up skin surfaceincludes the inner side surface. The down skin surfaceincludes the outer side surface. An inclination angle α of the down skin surfacewith respect to the horizontal direction is minimal at the end of the inlet. The inclination angle α is equal to or greater than 45 degrees. At the time of shaping, the support structuremay be shaped inside the target hole. The support structureis an elongated rod shape extending in the vertical direction. The support structureextends from the base surfaceor the up skin surfaceto the down skin surface.

Next, a cavitation processing apparatus for cavitation processing will be described. As shown in, a cavitation processing apparatusincludes a tank, the nozzle, a fixing base, and a high-pressure fluid supply source (not shown).

The tankstores the processing liquid. The processing liquidis, for example, water. The processing liquidis obtained by suspending the abrasives. The tankmay include a device for circulating the stored processing liquid.

The nozzleis connected to the high-pressure fluid supply source. The nozzlehas an ejection port. The ejection portfaces vertically downward. The nozzleejects a jet Cof the processing liquidvertically downward from the ejection port. The jet Cis a linear rod-shaped jet. The jet Cincludes lots of cavities. The nozzlecan move in three axial directions in the horizontal direction (the front-rear direction and the left-right direction) and the vertical direction. The ejection velocity (pressure) of the jet Cand the three-axis movement of the nozzleare controlled by a control device (not shown).

The fixing basefixes the workpiece. The workpieceis fixed to the fixing baseby fasteners (not shown) such as bolts and clamps. The fixing baseis movable in the vertical direction. The workpieceis moved in and out of the tankby the vertical movement of the fixing base. The vertical movement of the fixing baseis controlled by a control device (not shown).

The cavitation processing apparatuscan eject the jet Cat any position of the workpiecefrom any distance.

Subsequently, the workpieceand the nozzleare immersed in the processing liquidin which the abrasivesare suspended.

First, the workpieceis fixed to the fixing base. The workpieceis fixed in a posture in which the inletof the target holefaces upward and the end portion of the inner side surfaceon the outletside is parallel to the vertical direction.

Next, the workpieceis immersed in the processing liquidstored in the tankby moving the fixing basedownward.

Next, the nozzleis moved so as to be immersed in the processing liquid, and an ejection direction of the jet Cis aligned with the ejection axis. The nozzleis located above the target hole. The position of the nozzlein the X direction is a position opposed to the end portion of the target holein the X direction.

Subsequently, the support structureis removed by cavitation processing.

First, the high-pressure fluid supply source is activated to eject the jet Cfrom the ejection portof the nozzlealong the ejection axis, as shown in. Preferably, the jet Cis a linear rod-shaped jet.

The jet Cincludes lots of cavities. The jet Centrains the abrasivesand impinges on the support structureand the side surfaceof the target hole. The abrasivescontained in the jet Ccauses the support structureto be folded or scraped off. After the support structureis removed, the side surfaceis smoothed by the abrasivescontained in the jet C. The side surfaceis peened by the impact force when the cavity included in the jet Ccollapses. The peening process imparts compressive residual stress to the side surface.

Next, as shown in, the nozzleis moved along the X direction in conformity with the shape of the target holewhile the jet Cis ejected. This allows the jet Cto reach the entire area inside the target hole. Preferably, the nozzleis moved while the jet Cis ejected, as shown by the arrow A.

In this way, the jet Cremoves the support structureacross the entire area inside the target hole. At the same time, the jet Csmoothes and peens the inner side surfaceand the outer side surfaceof the target hole.

As described above, in the present embodiment, the workpieceis shaped by additive manufacturing, and the support structureformed at that time is removed by cavitation processing to form a product. In the cavitation processing, by bringing the ejection axisclose to the inner side surfaceof the curved portion, the abrasiveswidely reaches, and the area where the jet Cacts is not biased toward the outer periphery of the curved portion, so that the entire area inside the target holecan be appropriately processed.

In the present embodiment, the ejection axisis along the inner side surfaceat the end portion of the target holeon the outletside. This promotes the peening processing of the region on the inner peripheral side of the curved portion. If the ejection axisis vertically downward, it is not affected by gravitational force, and the jet Ceasily reaches a target position. When the jet Cis a linear rod-shaped jet, the dynamic pressure of the jet Cincreases. This promotes the breakage and removal of the support structure. As the jet Chas a linear rod shape, the side surfaceis less likely to be deformed.

The cavitation processing method according to a second embodiment will be described. The present embodiment differs from the first embodiment in the shapes of a workpiece. As shown in, the workpieceof the present embodiment has a single target hole. The target holehas a circular cross-section. The target holehas an inlet, an outlet, and a side surface. The target holeincludes an upper straight portion, a curved portion, and a lower straight portion. The upper straight portionextends linearly in an obliquely downward direction (a leftward downward direction in) inclined from the inletto −Y direction. The curved portionis curved in an obliquely downward direction (a rightward downward direction in) inclined in the +Y direction from the lower end of the upper straight portion. The lower straight portionextends linearly from the lower end of the curved portionto the outletin an obliquely downward direction (a rightward downward direction in) inclined in the +Y direction. In, the line segment Lindicates a border between the upper straight portionand the curved portion. The line segment Lindicates a border between the curved portionand the lower straight portion. The curved portionincludes an inner side surfaceand an outer side surface. The lower straight portionhas a lower inner surface. The lower inner surfaceis a surface that is connected to the inner side surface

As shown in, the ejection axisis defined in a cross section passing through the central axis of the target hole. The ejection axishas at least a portion that is closer to the inner side surfacethan the outer side surfaceof the curved portion. The ejection axisextends along the inner side surfaceat the outletside from the end of the inletof the curved portion. The ejection axispasses through the inlet. The angle β between the ejection axisand the lower inner surfaceis preferably as small as possible. The ejection axismay be a straight line that enters the target holefrom the inletand exits to the outlet. The ejection axismay be a straight line that enters the target holefrom the inletand intersects the side surfaceof the target hole

Also in the present embodiment, the cavitation processing apparatussubstantially the same as that of the first embodiment is used. The step of the cavitation processing method according to the present embodiment is different from that of the first embodiment only in that the nozzleis not moved in the X direction.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention, and all technical matters included in the technical idea described in the claims are the subject of the present invention. While the above embodiments have been shown by way of example, those skilled in the art will recognize that various alternatives, modifications, variations, and improvements can be made from the disclosure herein, which fall within the scope of the appended claims.